A ball joint for movably connecting shaft-like components to each other is conventionally used in suspensions and steering mechanisms for vehicles such as automobiles. A ball joint is generally configured such that a spherical ball portion formed at an end of a shaft-like ball stud is slidably held within a metal socket with a resin ball seat (also referred to as a bearing seat) placed between the ball portion and the socket. The ball joint is provided with a dust cover for covering at least an opening of the ball seat so that foreign matter such as water droplets or powder dust is prevented from entering the socket within which the ball portion slides.
For example, below-described Patent Document 1 discloses a ball joint having a rubber dust cover attached to the outer periphery of an opening portion of a resin ball seat which projects from a socket.